Harvest-Aid Efficiency in Guar (Cyamopsis Tetragonoloba (L.) Taub.) in the Texas Plains

Home , Crop desiccation, Guar

Harvest-aid Efficiency in Guar (Cyamopsis tetragonoloba (L.) Taub.) in the Texas Plains

Jonathan Shockey BS

A Thesis

Plant and Soil Sciences

Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of

MASTERS OF SCIENCE

Approved

Dr. Peter Dotray Chair of Committee

Dr. Calvin Trostle

Dr. Noureddine Abidi

Mark Sheridan Dean of the Graduate School

December, 2016

Texas Tech University, Jonathan Shockey, December 2016

Acknowledgements

I would like to thank Dr. Calvin Trostle and Texas A&M AgriLife Extension for not only his guidance during this research and for allowing me the time away from my assigned duties to complete these experiments; but also for providing the funding to get it accomplished. Under his direction I learned many things about agricultural research that

I will carry with me throughout my career. I would also like to thank Dr. Peter Dotray for his advice and direction both as committee co-chairman and as an instructor for modes and mechanisms of herbicides. Rounding out my committee I would like to thank

Dr. Noureddine Abidi for his expert advice in all potential biopolymer aspects of this study, and patient instruction during his biopolymers and bioproducts course.

Additionally, I would like to thank Ray White for his assistance in conducting spray applications, harvesting, and other data collection, his time and dedication to this research was without question a major contribution to its completion. I would also like to thank Dr. Katie Lewis for her expert assistance with SAS and other software questions.

Likewise, I would like to extend a heartfelt thank you to all the producers and research colleagues who allowed me to invade their fields to conduct my research. This list includes Dr. Paul Delane, Clint White, Curtis Erickson, Will Cozart, and Donald Kirksy.

I would also like to thank Dr. Lewis Norman of United Guar LLC, and Alex Muraviyov of Guar Resources LLC for technical guidance from the guar industry.

Last but not least, I would like to thank my family for their love, support, and patience through this long process. The most patient of all, my loving wife Emily, son

Paxton, and daughter Maddison, I did this for you, thank you.

Texas Tech University, Jonathan Shockey, December 2016

Table of Contents Acknowledgements………………………………………………………………………ii Abstract…………………………………………………………………………………..iv List of Tables...…………………………………………………………………………..vi List of Figures…………………………………………………………………………..vii I. Introduction……………………………………………………………………………1 II. Literature Review…………………………………………………………………….5 2.1 Guar Production……………………………………………………………….5 2.2 Harvest Aid Chemicals………………………………………………………11 2.3 Guar seed and Gum…………………………………………………………..16

III. Materials and Methods…………………………………………………………….20 3.1 Harvest Aid Efficiency………………………………………………………24 3.2 Harvest Aid Timing…………………………………………………...... 25 3.3 Black Seed Measurements…………………………………………………..26

IV. Results and Discussion……………………………………………………………..27 4.1 Harvest Aid Efficiency………………………………………………………27 4.2 Harvest Aid Timing………………………………………………………….38 4.2.1 Early Application Results……………………………………………...38 4.2.2 Optimal Application Results.…………………………………………..46 4.3 Black Seed Results…..…………………………………………………...56

V. Summary and Conclusions………………………………………………………....59 Bibliography…………………………………………………………………………….61

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Texas Tech University, Jonathan Shockey, December 2016

Abstract

The regions known as the Texas High and Rolling Plains are considered arid or semi-arid climates. These regions receive less than 25 cm, and 25 to 50 cm of rainfall annually. However, despite these climatic disadvantages the large portions of arable lands in these regions are put to use in crop production. The major crops of these regions are cotton (Gossipium hirsutum (L.)), wheat (Triticum aestivum (L.)), irrigated peanuts

(Arachis hypogeae (L.)), irrigated corn (Zea maizes (L.)), and sorghum (Sorghum bicolor

(L.)) as well as many other lesser grown alternative crops.

Due to current climatic changes as well as depletion of ground water producers have begun to alter traditional farming practices by adopting new practices such as cover cropping, no-till farming, and crop rotation with more drought tolerant crops to maintain profitability and sustainability. Some producers are turning to guar, Cyamopsis tetragonoloba (L.) Taub., as a crop to be placed in a rotation with less water efficient crops as well as a catch crop after a failed first crop. Although guar is a drought tolerant legume, production is not without obstacles. Guar has an indeterminate grow habit and the stem tends to remain moist well after a hard freeze, lengthening the time harvestable yield is left in the field to weather and diminish in both quality and quantity. The use of herbicides known as harvest aids has the potential to alleviate some of these issues by artificially drying the crop earlier than would be possible by natural means.

Two different trials were conducted to determine the efficacy of seven commercial harvest aids in guar and to determine proper timing of application of these harvest aids. Herbicidal activity of these chemicals was evaluated at 0, 7, 14, and 28 days

Texas Tech University, Jonathan Shockey, December 2016 post treatment by rating treated plots for color change, percent green pods remaining, percent terminal growth remaining, and the occurrence of regrowth. In addition to activity ratings yield and weathered seed measurements were also collected.

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List of Tables 2.1.1 Seasonal averages for temperature and precipitation for the Texas High Plains……………………………………………………………………………..10 2.1.2 Seasonal averages for temperature and precipitation for the Texas Rolling Plains……………………………………………………………………………..11 2.2.1 General information for herbicides evaluated.…………….……………………..14 3.1 Agronomic data for each trial ……………………………….………..…………21 3.2 Whole Plant Color Ratings....………………………………...………………….22 3.3 Regrowth Ratings……...………...….……………………………………………23 3.1.1 Harvest aid suggested and applied rates for guar……,…………………………..24 4.1.1 Average Color Ratings…..…………………... ………………………………….29 4.1.2 Average Green Pod Percent...………….………………………………………...31 4.1.3 Average Percent Terminal Growth..……………………………………………..33 4.1.4 Average Regrowth Ratings....……………………………………………………35 4.1.5 Average Bushel Weight and Average kg per Hectare...………………………....37 4.2.1.1 Average Color Ratings for Early Applications…………………………………..39 4.2.1.2 Average Green Pod Percent for Early Applications...... ….42 4.2.1.3 Average Percent Terminal Growth for Early Applications……………………...44 4.2.1.4 Average Regrowth Ratings for Early Applications………..………...…………..45 4.2.2.1 Average Color Ratings for Optimal Applications…………………..…………...48 4.2.2.2 Average Green Pod Percent for Optimal Applications………………………...... 50 4.2.2.3 Average Percent Terminal Growth for Optimal Applications…………………...52 4.2.2.4 Average Regrowth Ratings for Optimal Applications…………………………...54 4.2.2.5 Average Bushel Weight and Average kg per Hectare for Timing Applications...55 4.3.1 Average Black Seed Percentages for Efficacy Trials……………………………56 4.3.2 Average Black Seed Percentages for Timing Trials………….………………….57

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List of Figures 3.1 Examples of color difference between the untreated control and the active ingredient paraquat at 7 days post application...…………………………………23 4.1.1 Average Color Ratings.…………………………………………………………..29 4.1.2 Average Green Pod Percent…………………..………………………………….32 4.1.3 Average Terminal Growth Percent...…………………………………………….34 4.1.4 Average Regrowth Ratings……………………………………………...……….36 4.1.5 Average Bushel Weight and kg per Hectare……………………………………..37 4.2.1.1 Average Color Ratings for Early Applications…………………...……………...40 4.2.1.2 Average Green Pod Percent for Early Applications……………………………..42 4.2.1.3 Average Terminal Percent for Early Applications……………………………….44 4.2.1.4 Average Regrowth Ratings for Early Applications……………………………...46 4.2.2.1 Average Color Ratings for Optimal Applications……………………………….48 4.2.2.2 Average Green Pod Percent for Optimal Applications………………………….50 4.2.2.3 Average Terminal Percent for Optimal Applications……………………………52 4.2.2.4 Average Regrowth Ratings for Optimal Applications…………………………...54 4.2.2.5 Average Bushel Weight and kg per Hectare for Timing Applications…………..55 4.3.1 Average Black Seed Percent for Efficacy Trials…...……………………………56 4.3.2 Average Black Seed Percent for Timing Trials……………………..…………...57

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Chapter I

Introduction

Guar, or clusterbean, is an annual legume grown in the semi-arid regions of India,

Pakistan, and the American southwest. It is grown as green manure, animal fodder, as a

green vegetable, and for the galactomannan (GM) content of the seeds, known as guar

gum (Pathak, 2015). Guar was first introduced to the United States in 1903, mainly for

use as a soil-building legume and emergency cattle grazing crop that was well suited to

the arid climates of the Southwest (Whistler & Hymowitz, 1979). However, it was not

until World War II, when locust bean gum, used as a binder in the paper industry, became

scarce that guar was investigated for potential industrial uses, and this has been the crop’s

major area of contribution ever since (Whistler & Hymowitz, 1979). Since then the

major United States production area is a region encompassing southwestern Oklahoma

and central and western Texas known as the Rolling and High Plains respectively.

Galactomannan is a non-starch polysaccharide consisting of a β-(1-4)-D-mannan backbone with single molecule α-(1-6)-D-galactose side branches found primarily in the endosperm of many legume species (Prajapati et al., 2013; Wu, Cui, Eskin, & Goff,

2009). These polysaccharides have a high affinity to water and therefore form extremely viscous solutions at most concentrations without forming a gel (Wu et al., 2009).

Galactomannans come from four major sources: locust bean (Ceratonia silique (L.)), guar, tara (Caesalpinia spinose (Molina) Kuntze), and fenugreek (Trigonella foenum- graecum (L.)), each differing from one another in the galactose to mannose ration (G/M), and molecular weight (Liyanage, Abidi, Auld, & Moussa, 2015; Prajapati et al., 2013;

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Wu et al., 2009). This ratio is directly related to the molecular weight and corresponding size of the galactomannan molecule, and also has distinct effects on the rheological properties, such as emulsion and viscosity, of the solutions made from each type of gum.

The seeds of guar contain approximately 15% hull, 45% embryo, and 40% endosperm, with a G/M ratio of 2:1 (Liyanage et al., 2015; Prajapati et al., 2013). The endosperm is

the portion of the seed containing the majority of the galactomannan, and it is from this

source that the gum is extracted for industrial uses. The main purpose for the endosperm

within the seed is to serve as a food source for germinating embryos and to prevent

complete desiccation by retaining water within the seed (Srivastava & Kapoor, 2005).

Galactomannan gums, or seed gums, are gaining importance because they are

natural products that are renewable, ecologically friendly, and are generally recognized as

safe (Srivastava & Kapoor, 2005). In recent years the importance of guar as an industrial gum crop has grown substantially, mostly due to its use by the oil and gas industry. Guar gum is used as a viscosity increasing additive in fracturing fluids for the process used to release fossil fuels trapped in layers of rocks, known as hydraulic fracturing. Guar gum is also used in pharmaceuticals and food processing; it can be found in many common household items from ice cream to hand lotion. Unlike locust bean gum guar gum does not possess gelling properties even at high concentrations (Srivastava & Kapoor, 2005).

In times of decreased supply or high guar gum prices the gums of Sasbania bispinosa,

and Cassia tora have been used as replacements for industrial uses only, not food

(Mathur & Mathur, 2005). These plants are both wild weeds native to India, and are

mainly used for land reclamation and have not been studied sufficiently to determine

human toxicities.

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Guar as a crop has an indeterminate growth habit and if fall weather conditions

stay favorable for growth plants, especially the stalks, will remain moist and green for

one month or more after a hard freeze. A hard freeze is defined by the National Oceanic

and Atmospheric Administration (NOAA) as conditions when temperatures drop to or

below -2 C for two or more hours during the growing season. This lack of drydown, or

even extended growth, often results in harvest delays of 1 to 2 months where mature

harvestable yield is subject to environmental weathering and degradation. Due to wetter

weather patterns in the fall and early winter in the Texas and Oklahoma plains this delay

in harvest can result in lowered seed quality and potential price reduction when selling

the harvested yield. One possible solution to this issue is to enlist the use of chemical

harvest aids. These contact, non-selective herbicides act as plant desiccants halting

growth and drying the plant in order to allow for earlier and potentially more profitable

and productive harvesting.

Harvest aids are employed in many different crops such as cotton, sunflowers

(Helianthus annuus (L.)), and soybeans (Glycine max (L.) Merr.) to terminate growth and

effect timely harvest (Griffin, Boudreaux, & Miller, 2010; Johnson & Peterson, 2007;

Kelley, Keeling, Keys, & Morgan, 2015). Most harvest-aid active ingredients work by causing lipid peroxidation resulting in the destruction of cellular membranes. Many are fast acting, as is the case with chemicals such as paraquat that can show symptoms of cell membrane damage within 1 to 2 hours of application if weather conditions are conducive.

However, most active ingredients used in this study showed visual symptoms in 7 to 14 days.

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Another reason behind the interest in harvest aid use in guar is to reduce the

quantity of black seeds produced by the crop. Seed color of guar ranges from dull-white

to black. Late season cool, wet weather events have been observed to increase the

percentage of black seeds harvested during the current research. Guar gum industry’s

perception is that black seeds are of poor quality due to seed coat degradation thus

meriting price discounts to producers. However, it has been reported that though black

seeds contain less seed coat when compared to dull-white seeds, there was no significant

difference in endosperm content between the two colors (Liu, Peffley, Powel, Auld, &

Hou, 2007).

The goal of this study was to determine the efficiency of plant desiccation of

seven commercial harvest-aids when applied to guar. The research also attempted to

distinguish any yield and seed coat color changes that could be attributed to a particular

active ingredient. Active ingredients used in this study were: paraquat, sodium chlorate,

diquat dibromide, carfentrazone-ethyl, glufosinate, glyphosate, and pyraflufen-ethyl.

Paraquat and sodium chlorate labels list guar in the harvest aid section. Carfentrazone- ethyl is labeled for hooded post emergence-directed applications only, and glyphosate is also labeled for hooded post emergence-directed applications as well as preplant and post-harvest applications. In addition to efficacy of the seven listed active ingredients, an investigation into application timing of the two chemicals labeled for harvest aid use and glyphosate was conducted to determine possible effects on yield and seed quality.

Finally, in an attempt to address the black seed concerns, a percent black seed measurement was collected for each harvested sample for comparison across treatments.

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Chapter II

Literature Review

2.1 Guar Production

Guar, Cyamopsis tetragonoloba (L.) Taub., is adapted to arid and semi-arid climates with high temperatures and dry conditions; the plant can stop growing during moisture-limited time periods and continue growth when ample moisture is available

(Undersander et al., 1991). For these reasons it is well-suited for the Texas plains either as a main crop or as a catch crop after a failed initial crop such as cotton (Gossipium hirsutum (L.)). Due to guar’s role as a minor crop there has been little agronomic research conducted since the early 1970’s. However with the relatively new role as an industrial gum crop supporting the petroleum industry there is a growing interest in not only the agronomics and genetic improvement of guar, but also the chemistry of the gum produced from its seeds.

Worldwide the vast majority of guar production takes place in the arid regions along the border between India and Pakistan. More than 80% of global production comes from the region known as the Thar Desert (Liyanage et al., 2015). In this region guar is grown as a kharif or monsoon crop, meaning it is planted after the end of the seasonal rainy period (Kumar, 2015). Due to this dependence on rainfed conditions, planted area and yield varies drastically from year to year (Yadav & Shalendra, 2014). Even so, yields from 2001 to 2011 averaged 1.22 million tons of seed over 2.96 million hectares

(Liyanage et al., 2015). This is about half the average per hectare yield for guar production in the United States of 900 kg per hectare (Trostle, 2013a).

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Guar is hypothesized to have originated in Africa due to the presence of a related species known locally as barasan, Cyamopsis senegalensis, and was possibly domesticated in Africa or Arabia and introduced into India through the horse trade, as it was brought as horse fodder (Pathak, 2015). Historically guar was grown as both animal fodder and as a protein source for vegetarian diets (Liyanage et al., 2015). It is also used as a medicinal herb and to shade ginger in intercropping systems (Whistler & Hymowitz,

1979). Though still grown for many of these traditional purposes, the area under cultivation and popularity of the crop have increased dramatically since the discovery of the seed’s gum content and its potential as an industrial crop. In many areas of production guar is now grown as part of a crop rotation system. In India it is the preferred crop for use in rotations with other grains such as wheat and pearl millet, allowing for optimal water usage and increase soil quality and yields for crops following guar (Pathak, 2015).

In the American southwest guar is grown less as a primary crop and more as a catch crop when primary crops fail or weather prevents timely planting of the primary crop. Guar production in the United States is based on contracts that define price, discounts, delivery points, and acceptable grades (Trostle, 2012). Very few producers plant guar without first having a contract for the purchase of the seed harvested, and in general guar is a rotation crop that is not continuously grown due to low gross income.

Depending on variety guar has a growing season ranging from 80 to 150 days

(Undersander et al., 1991). Also, contributing to this role, as a drought and heat tolerant secondary crop, optimal germination soil temperatures need to be 21 C (Dennis & Ray,

1982). This usually occurs by late May in the Texas plains. In this region June plantings

Texas Tech University, Jonathan Shockey, December 2016 yielded more reproductive buds than July plantings (Rogers, 1973). Optimal planting depth of guar is 2.5 to 4 cm, planted at 4 to 6 kg of seed per hectare (Tripp, Lovelace, &

Boring III, 1977). When conditions are right guar can germinate and emerge in 4 to 6 days after planting (Pathak, 2015). During this research that guar planted in optimum field conditions at the Texas A&M AgriLife Research & Extension Center in Lubbock

Texas, was 85% emerged in 3 days during the 2014 growing season.

Guar performs best on sandy loam soils with a pH ranging from 6.5 to 8.0 (Tripp et al., 1977). It is also tolerant to soil salinity and alkalinity (Undersander et al., 1991).

Due to susceptibility to seedling diseases soils need to be well drained as guar has trouble growing in waterlogged or flooded soils (Pathak, 2015). Guar has a deep taproot and has excellent soil building properties, such as aggregation and potential nitrogen fixation; because of this it works well in rotation programs with other arid crops such as cotton, grain sorghum, and small grains (Tripp et al., 1977). Since guar is a legume it has the ability to fix atmospheric nitrogen when the roots are infected with guar-specific

Rhizobium spp. bacteria. Guar seed can be inoculated with the bacteria mainly using seed box powders. It has been observed in the High Plains region of Texas there is little to no infection or subsequent nodulation on the roots of inoculated guar, causing many producers to forego this practice. Additionally there are currently no guar-specific commercial inoculants available in the United States.

Guar is a heat and drought tolerant crop. It performs best in areas receiving 50 to

76 cm of annual rainfall (Tripp et al., 1977). In areas where waterlogging is not likely and moisture is adequate guar can be planted on flat ground. However, guar is normally planted on raised seed beds to both provide adequate drainage and allow for better

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mechanical harvesting of lower branches (Tripp et al., 1977; Undersander et al., 1991).

Depending on seedbed preparation and desired row spacing available guar is usually

planted either with a grain drill or vacuum planter. Plate planters can be used but due to

heavy seed weights seed boxes should not be filled completely to avoid clogging of the

plates (Undersander et al., 1991). Optimal row spacing for guar is 76 to 101 cm. Due to

the lack of post-emergent herbicides fields should be weed free (Tripp et al., 1977;

Undersander et al., 1991). Weeds pressure and competition can greatly reduce seed

yields, therefore, the labeled preplant incorporated herbicide trifluralin is recommended

to reduce early season weeds (Tripp et al., 1977). Quality seed production is limited in regions with high rainfall and humidity due to the shriveling and blackening that can occur if these conditions are present after maturity (Liu et al., 2007; Tripp et al., 1977).

Guar is susceptible to many diseases known to affect crops in Texas and

Oklahoma such as Alternaria leaf spot and bacterial blight. Instances of disease can be

worsened or caused by cool late season rains or overhead irrigation after flowering. Guar

can also be infected by cotton root rot (Phymatotrichum omnivorum). However due to its

resistance to the pathogen the disease seldom causes death (Tripp et al., 1977).

Alternaria leaf spot is a fungal disease that causes round brown lesions that progress until

the entire leaf is infected and eventually senesced (Yadav & Shalendra, 2014). Bacterial

blight is a seed borne disease that is of the greatest importance in guar production. It

causes angular lesions on the leaves and black streaking of the stem followed by wilting,

leaf senescence, and plant death (Pathak, 2015).

In the United States guar is mechanically harvested using grain combines. Due to

the brittleness of the pedicel of dry pods and the amount of plant material taken into the

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machinery, to ensure an efficient harvest there are many machine settings that must be

adjusted on the combine. Ground speed should be slow not exceeding 5 km per hour for

harvesting guar (Undersander et al., 1991). The reel should be extended to 15 to 30 cm in front of the cutter bar and set to just slightly faster than the ground speed of the combine

(Tripp et al., 1977). Since the seed is heavy fan speeds can be set quite high to aid in trash removal (Tripp et al., 1977; Undersander et al., 1991). Cylinder speeds should be at

500 to 600 rpms with the concave set at 2 mm or (Dennis & Ray, 1982).

Many producers and contract guar production companies have custom harvesting companies that harvest guar in the Texas plains. Most of these custom operations have air reels to aid in catching pods that break from the plants as the cutter bar cuts them.

These new header attachments have the potential to increase captured yield by as much as 56 kilograms per hectare (Liyanage et al., 2015). Though no official state or USDA data is available, guar yields for United States production average about 1000 kilograms per hectare on dryland, and 1700 kilograms per hectare under irrigation, though full irrigation is not recommended due to disease issues and crop physiology (Trostle, 2013a).

The climate in which guar is grown in the United States is similar climatically to the area from which the crop originated. The National Environmental Satellite, Data, and

Information Service (http://www.ncdc.noaa.gov/climate-information/climate-us) reports

Lubbock, in the High Plains region of Texas (elevation of 992 meters sea level) has an average annual temperature, 1981-2010, of 16 C, and average annual rainfall of 49 cm.

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Table 2.1.1 Seasonal averages for temperature and precipitation for the Texas High Plains.

Average Average Seasonal Seasonal Average Average Max Min Seasonal Seasonal Season Temperature Temperature Temperature Precipitation C C C cm

Winter 13 -2 5 6

Spring 24 8 16 12

Summer 36 19 26 17

Fall 23 8 16 13

Alternatively, the National Environmental Satellite, Data, and Information

Service (http://www.ncdc.noaa.gov/climate-information/climate-us) reports Vernon

(elevation of 368 meters), in the Rolling Plains region of Texas with an average annual temperature, for the same time period, of 17 C, and an average annual rainfall of 71 cm with higher seasonal averages than Lubbock (Table 2.1.2).

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Table 2.1.2 Seasonal averages for temperature and precipitation for the Texas Rolling Plains.

Average Average Seasonal Seasonal Average Average Max Min Seasonal Seasonal Season Temperature Temperature Temperature Precipitation C C C cm

Winter 13 -2 6 10

Spring 24 10 17 20

Summer 35 21 28 23

Fall 25 11 18 19

2.2 Harvest Aid Chemicals

Harvest aid chemicals are contact herbicides normally used to desiccate crops to improve harvest efficiency and quality. In grain crops desiccants are not only used to dry crops but also to dry late season weeds that may affect grain moisture. By increasing moisture these weeds can damage harvested grain as well as reduce harvest efficiency

(Griffin et al., 2010). Grain that is too moist increases the potential for post-harvest losses from spoilage due to bacterial and fungal growth as well as aflatoxin contamination (Stichler & Livinston, 2003). When used in grains careful timing of harvest aid application is of utmost importance. To ensure there is no loss in seed yield or quality seed must be physiologically mature before harvest aid application (Boudreaux

& Griffin, 2011).

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According to the 2015 High Plains and Northern Rolling Plains Cotton Harvest-

Aid Guide (Kelley et al., 2015), a common cotton management practice in the

Southwestern United States uses chemical harvest aids applied at 4 nodes above cracked boll in order to hasten the maturity of a cotton crop and reduce potential pre-harvest losses. These cotton harvest aids are used to reduce losses of lint yield, fiber quality, and seed quality due to environmental weathering of fiber and seed. This research stresses the importance of timely harvest aid applications to optimize yield and quality variables, and that determining crop maturity is critical to successfully use harvest-aids as a tool to increase high quality lint yields.

Factors that increase the performance of harvest aids include: warm, calm, sunny weather, low soil moisture but not low enough to stress the crop, and little to no secondary growth (Kelley et al., 2015). Possible factors that are detrimental to harvest- aid performance are: applications made during cool, cloudy conditions; wet weather after application; plant moisture stress at the time of application; and poor spray coverage

(Kelley et al., 2015).

Among agricultural herbicides that are classified for use as harvest-aids for cotton there are three main types; desiccants, defoliants, and boll openers (Kelley et al., 2015).

The use of each type is dependent on crop maturity, weather, amount of green leaves the crop contains, and potential profitability. Desiccants which dry green plant material and defoliants which halt growth and cause leaf senescence, as well as several other categories of contact herbicides were evaluated in the current research.

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Herbicides are also used as harvest aids in grain crops such as sunflowers, corn,

grain sorghum, soybeans, dry beans, castor, and guar. In sunflowers, desiccants such as

paraquat and sodium chlorate are used to reduce yield losses due to plant lodging, seed

shatter, and bird damage (Johnson & Peterson, 2007). Before the advent of herbicide-

tolerant corn glyphosate was used to increase the rate of kernel drying and reduce weeds

such as quackgrass before harvest (Alcantara & Wyse, 1988). Sodium chlorate, and

glyphosate are both used to dry late season weeds and hasten sorghum harvest after seed

maturity (Stichler & Livinston, 2003). In soybeans for both determinate and

indeterminate varieties, paraquat and carfentrazone-ethyl are widely used to dry leaves

and stems of the crop after seed pods have matured and dried (Boudreaux & Griffin,

2011). Glufosinate, glyphosate, and paraquat are used as harvest aids in dry beans such

as light red kidney beans (Wilson & Smith, 2002). Paraquat and pyraflufen-ethyl were tested to determine seed yield and quality effects in early termination of castor, and paraquat was found to be effective in both drying the plants and preserving seed yield and quality (Rieff, 2011). Finally, paraquat and sodium chlorate are used to dry stems and leaves in guar to effect timely harvest and preserve seed quality (Trostle, 2013b).

The herbicides used in the current study can be grouped by common mode of action (Table 2.2.1). Paraquat and diquat dibromide are photosystem one (PSI) inhibitors. Carfentrazone-ethyl and pyraflufen-ethyl are protoporphyrinogen oxidase

(PPO) inhibitors. Glyphosate and glufosinate are amino acid synthesis inhibitors. And finally, sodium chlorate, an inorganic herbicide, is a readily absorbed highly active oxidizing agent in plants.

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Table 2.2.1 General information for herbicides evaluated in this study.

Labeled for Use Preharvest as a Harvest Interval Commercial Active Ingredient Mode of Aid in Guar (PHI) in Product Name Action (Y/N) Days

Defol 5 Sodium Chlorate Oxidizing Y 7-10 Agent

Gramoxone SL 2.0 Paraquat PSI Inhibitor Y 7

Reglone Diquat PSI Inhibitor N 7 dibromide

Aim EC Carfentrazone- PPO Inhibitor N (Labeled for 3 ethyl hooded or post directed applications)

ETX Pyraflufen-ethyl PPO Inhibitor N 7

RoundupPowerMax Glyphosate Amino Acid N 7 Synthesis Inhibitor

Liberty Glufosinate Amino Acid N 70† Synthesis Inhibitor † This is the preharvest interval for over the top tolerant soybean and corn application for feed and food stuffs, more research would be required to determine if this is necessary for industrial non- food guar gum production.

PSI Inhibitors

Photosystem one (PSI) inhibitors, paraquat and diquat dibromide, belong to the bipyridilium class of herbicides (Anderson, 2007). In general these compounds are highly soluble in water and form strong cation complexes that are readily absorbed into foliage (Dotray, 2015). Due to its high mammalian toxicity paraquat is listed as a

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restricted use herbicide, whereas diquat dibromide is listed as a general use herbicide

(Shaner, 2014). Affected green plants are killed in 1 to 2 days, and dried enough to

harvest in 7 to 10 days; their action is more rapid when exposed to sunlight (Anderson,

2007; Dotray, 2015). Visual damage from PSI herbicides begin as water soaking or dark

green lesions on the leaf surface followed by necrosis and death, and these effects are

intensified in high light conditions (Peterson, Thompson, Shoup, & Jugulam, 2015).

These chemicals disrupt PSI by accepting electrons from the PSI electron transport chain to become free radicals (Dotray, 2015). These free radicals then react with water to form superoxide, which then reacts with an enzyme, super oxide dismutase, to form hydrogen peroxide, which further reacts with the cell membrane leading to lipid peroxidation and membrane destruction (Anderson, 2007; Dotray, 2015).

PPO Inhibitors

Protoporphyrinogen oxidase inhibitors, or PPO inhibitors, used in this study were carfentrazone-ethyl and pyraflufen-ethyl. These two herbicides cause rapid necrosis and desiccation of plant tissue. Carfentrazone-ethyl is a general use herbicide, and pyraflufen-ethyl has no designation at this time (Shaner, 2014). The mechanism of action of a PPO inhibitor herbicide is to cause a buildup of protoporphyrinogen IX in the cytoplasm by blocking its conversion to another precursor of chlorophyll in the chain of reactions of the chlorophyll biosynthesis pathway (Dotray, 2015). Protoporphyrinogen

IX is highly reactive in light and once outside of the reaction center reacts with oxygen and light to form singlet oxygen, which initiates lipid peroxidation and cell membrane destruction (Dotray, 2015; Peterson et al., 2015).

Texas Tech University, Jonathan Shockey, December 2016

Amino Acid Biosynthesis Inhibitors

Two amino acid biosynthesis inhibitors were also investigated in this research, glyphosate, and glufosinate. Glyphosate inhibits the function of the enzyme enolpyruvyl shikimate-3-phosphate (EPSP) synthase. Glufosinate inhibits glutamine synthase. Both are listed as general use herbicides (Shaner, 2014). Symptoms of these herbicides include yellowing of the foliage and chlorosis usually within 7 to 10 days after application (Shaner, 2014). Glyphosate binds with and stops the function of EPSP synthase in the production pathway of aromatic amino acids (Anderson, 2007). This reduction in amino acid production in turn inhibits protein production causing the disruption of cellular functions and death (Dotray, 2015). Glufosinate inhibits the production of the amino acid glutamine by binding to and inactivating the enzyme glutamine synthase, also leading to a reduction in protein synthesis and cell death

(Dotray, 2015).

Inorganic Herbicides

The final harvest-aid investigated in this study is sodium chlorate. Sodium chlorate acts much like paraquat of diquat dibromide in herbicidal activity by forming strong oxidizing agents in plants (Anderson, 2007; Shaner, 2014). Once it has been absorbed into the cell it is metabolized into its ions sodium and chloride; the latter being the oxidizing agent that causes lipid peroxidation, cell death, and plant desiccation

(Shaner, 2014).

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2.3 Guar Seed and Gum

Guar produces a dicotyledonous seed that is dull-white to black in color and oval to round in shape (Vishwakarma, Shivare, & Nanda, 2012). The seeds are produced in pods ranging from 3 to 5 centimeters in length, with 7 to 8 seeds per pod and a 100 seed weight of about 2.8 grams at 10% moisture (El-Daw, 1998; Pathak, 2015; Vishwakarma et al., 2012). Seeds are composed of three main components: seed coat, embryo, and endosperm. The endosperm is the seed portion containing the high value gum. By weight these components make up 14 to 17%, 35 to 42%, and 24 to 35%, respectively, of seed weight (Liu et al., 2007). The endosperm is composed of 78 to 82% gum or galactomannan (Vishwakarma et al., 2012). The embryo or germ and the seed coat are byproducts and are ground for use in animal feed stuffs and are known as guar meal

(Murwan, Abdelwahab, & Sulafa, 2012).

Industrial and food gums are sticky substances usually derived from natural sources such as plants and bacteria. Gums, including resin, latex, and rubber, have been used by civilizations since ancient times for food and medicinal purposes. The ancient

Egyptians used gums to bind wrapping cloths to mummies as well as in the embalming process (Pathak, 2015). The gum obtained from the endosperm of guar is known as guar gum, and is one of many natural gums of industrial and commercial importance. Guar gum, fenugreek gum, tara gum, and locust bean gum are all commercial galactomannans

(Wu et al., 2009). Galactomannan is a polysaccharide consisting of a mannan backbone with galactose side branches (Whistler & Hymowitz, 1979). Commercially available galactomannans differ from each other in their mannose to galactose ratio. This ratio also affects the properties of the solution when mixed with a solvent (Pathak, 2015; Wu et al.,

Texas Tech University, Jonathan Shockey, December 2016

2009). Wu et al., (2009) found that mannose to galactose ratios for fenugreek gum, guar gum, tara gum, and locust bean gum were 1:1, 2:1 3:1, and 4:1 respectively, and that intrinsic viscosities of solutions made with these gums ranked in the order of guar gum > fenugreek gum > tara gum > locust bean gum.

Since these gums are derived from seeds after harvest, protecting seed quality before harvest is of utmost importance. The seed of mature guar plants left in the field past the time when it is ready to harvest tends to darken, or turn black, with high humidity or rain events. This tends to be the case in the Texas plains where the majority of the crop remains in the field until after a killing freeze occurs in order to dry the stems of the plant and halt growth (Trostle, 2012). Once harvested the general process of obtaining guar gum from whole seeds is to clean, mechanically split the seed, separate the embryo and seed coat from the endosperm, and grind the endosperm in to powder

(Vishwakarma et al., 2012).

When black seed is processed to remove the germ and seed coat and access the galactomannan rich endosperm, fragments of the seed coat tend to become stuck to the endosperm (splits) reducing gum quality due to contamination (Trostle, 2012). These fragments of seed coat could be caused by the deterioration of the seed coat integrity from environmental weathering. Seed coats of black guar seed contain cracks that can be observed when viewed under a dissecting microscope (Liu et al., 2007). Due to this contamination, prices paid to producers can be docked when grain containing high amounts of black seed is delivered to the processor.

Texas Tech University, Jonathan Shockey, December 2016

However, due to seed coat deterioration black seeds imbibe water at a higher rate and germinate at 10 percent higher rate than the light colored counterparts (Liu et al.,

2007). Liu et al., 2007 also reported that galactomannan content was not significantly different between light and dark seeds, thus showing that gum quality is maintained in spite of prolonged weathering; but due to the difficulty in mechanically removing all the seed coat from the splits processors prefer the hard light colored seeds. Liu’s research suggested that if viewed from the perspective of gum quality alone this dockage is unnecessary. However, when considering higher contamination from seed coat fragments and added processing needed to remove this contamination some dockage may be deemed appropriate.

In the Texas Plains weather tends to be wetter in the fall and early winter and can bring about the deterioration of guar seed coats causing black seed and reduced revenue for producers who decide to wait up to a month or more after seed maturity for freezing weather to terminate their crop (Trostle, 2012). In many other crops, such as cotton, harvest-aids are applied to terminate the crop early and preserve the quality of the harvested yield (Kelley et al., 2015; Trostle, 2012). However, very few producers apply these techniques to a low-input, low-value crop like guar. The current research was conducted to investigate the efficacy of seven harvest aids when applied to guar, as well as comparing yields and black seed percentages within the harvested seed. In addition to efficacy studies, research was conducted to determine the effects of terminating the crop earlier than normally called for by harvest-aid labels.

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Chapter III

Materials and Methods

All trials were established in existing fields of Kinman guar in randomized complete block format with 3 replications. Plot size was 4 meters wide by 6 meters long, with 102 cm row spacing. These dimensions constitute a four-row plot in which all rows were sprayed, and data was collected on the center two rows. The Kinman variety was released in 1975 by the Texas Agriculture Experiment Station in Vernon and its cooperators within USDA and Oklahoma State University. It is a preferred variety in the

High Plains and Rolling Plains because it has some resistance to Alternaria and bacterial blights (Stafford, Kirby, Kinman, & Lewis, 1976). Trials were conducted in the growing seasons of 2014, and 2015 (Table 3.1). High Plains locations were planted in 2014 and

2015 at the Texas A&M AgriLife Research and Extension Center near Lubbock (TXLB),

Texas. Trials in the Rolling Plains were planted in 2014 at the Texas A&M AgriLife

Research Station near Chillicothe (TXCH), Texas; and in 2015 on two producer fields near Vernon, Texas (TXVN and TXCW). Soil types for the locations were Olton clay loam and Acuff loam in Lubbock, Abilene clay loam in Chillicothe, and the soil type in

Vernon was Miles loamy fine sand (S. S. Staff, 2013).

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Table 3.1 Agronomic data for each trial presented by year and location.

Efficacy Early Planting Optimal Irrigation Rainfall Pre-plant Location Year Spray Date Spray cm cm Herbicides Date Date 1.5 TXCH 2014 June 17 None October 16 12.7 40.1 l/Hectare 1.5 TXLB 2014 June 13 October 6 October 13 30 35.2 l/Hectare September September 1.5 TXLB 2015 June 15 30 31.8 21 28 l/Hectare

TXCW 2015 June, 24 October 6 October 14 None 8.1 None

TXVN 2015 June, 30 October 6 October 14 None 8.1 None

Efficacy trials were conducted in order to determine effective termination of

growth and desiccation of plant tissue for seven commercial herbicides. Along with

efficacy trials timing trials were conducted to determine optimal timing of applications

three selected herbicides from the efficacy group. At each location and for both trials

visual ratings were collected at 0, 7, 14, and 28 days after treatment (DAT). This time

frame was chosen to include a baseline, 0 DAT, and times at which expected herbicide

activity would be observed, 7 and 14 DAT, as well as a rating conducted one and two

weeks after which treated plots were harvestable to gauge potential for regrowth and

allow for the natural drying of the untreated control for comparison. Following the last

visual rating, samples were harvested from a two row by two meter area for each plot,

and yield per hectare, test weight, and black seed percent measurements were collected.

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Visual ratings were plant color, percent green pods, percent growing terminal, and regrowth. Ratings were collected on a whole plot basis. Color was rated on a 1 to 7 scale

(Table 3.2), and was based on overall color on a whole plant and plot level. Green pod measurements were based on the estimated percent green, moist pods remaining on plants within the plot. This assessment was a visual estimate determined by assessing the plot from lowest pods to highest mature pods, and determining the relative ratio of dry harvestable pods to green moist pods, and reported as a percent of total pods. Finally, percent terminal and regrowth were based on new or continued growth at the meristems and new growth at the nodes respectively. Regrowth was rated on a 0 to 3 rating scale based on Table 3.3. Labeled application timing for harvest aids labeled for guar state that applications should occur when 80% of the pods are dry. Statistical analysis for all trials was conducted using SAS 9.3 software using the GLIMMIX procedure, to determine significance and mean separations.

Table 3.2 Whole plant color ratings and the corresponding numeric value used to determine growth termination and crop desiccation in preparation for harvest.

Rating Color 1 Dark Green 2 Medium Green 3 Light Green 4 Green-Yellow 5 Yellow 6 Tan 7 Brown

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Table 3.3 Regrowth ratings accessed by visually determining the amount of new growth at the nodes of the plants and the corresponding numeric values for each level of regrowth present.

Rating Regrowth 0 None 1 Trace 2 Moderate 3 High

Untreated Paraquat

Figure 3.1 Examples of color difference between the untreated control (left) and the active ingredient paraquat (right) at 7 days post application. At this time the control has a color rating of 4 or green-yellow and paraquat had a color rating of 7 or brown.

Harvest samples were collected by hand from a two row by two meter area and

threshed using an 18 Inch Bundle Thresher (Kincaid Equipment Manufacturing, Haven,

KS, USA). Samples were then cleaned using a Clipper Office Tester (A. T. Ferrell

Company, Inc., Bluffton, IN, USA) to remove plant debris. Sample moisture was then

measured with a Model SL95 moisture meter, using the sorghum setting, (The Steinlite

Corporation, Atchison, KS, USA) and a volume of 250 ml was weighed to calculate

bushel weight by determining the dry weight of each sample based on the moisture

Texas Tech University, Jonathan Shockey, December 2016

measurements and then calculating bushel weight in grams per bushel based on this

adjusted weight of a 250 ml volume sample from each plot. The dry weights were also used to calculate overall yield in kilograms per hectare adjusted to 12 percent moisture.

This moisture level is a grain industry standard moisture level; these calculations were required due to the absence of a USDA guar grain standard like those available for other grain crops.

3.1 Harvest Aid Efficacy

Efficacy trials consisted of seven different active ingredients plus an untreated control applied at labeled rates for comparable crops such as soybean or dry beans if no rate was provided for guar specifically and a carrier volume of 140 L per hectare (15 gallons per acre) (Table 3.1.1).

Table 3.1.1 Harvest aid suggested and applied rates for guar. Labeled Rate Adjuvants Labeled for Range Mixed Guar Harvest Active Ingredient L per Hectare L per Hectare with Spray Aid (Y/N) Used Sodium Chlorate 14 9 - 15 None Y Glyphosate 2.34 1.8 - 3.2 None N Diquat dibromide 2.34 1.7 - 2.3 0.25% NIS N Paraquat 2.34 1.7 - 2.3 0.25% NIS Y Carfentrazone-ethyl 0.14 0.14 0.25% NIS N Pyraflufen-ethyl 0.14 0.14 1 -2 % N COC Glufosinate 2.12 2.1 3.34 kg/H N AMS † Table___ contains a list of harvest aids, adjuvants, and rates applied; with herbicides labeled as harvest aids in guar identified. † Table___ - Adjuvants listed were required by the product label and are defined below. ‡ NIS - Non-ionic surfactant at .25% total spray volume. ‡ COC - Crop Oil Concentrate at 1-2% total spray volume. ‡ AMS - Ammonia sulfate salt.

Texas Tech University, Jonathan Shockey, December 2016

Crop maturity was targeted at 80% dry mature pods for harvest aid application and Day 0 ratings were taken immediately prior to harvest aid application. Applications were made with a carbon dioxide pressurized backpack sprayer (R&D Sprayers,

Bellspray, Inc., Opelousas, LA) with a two meter (80 inch) hand-held boom using

TeeJet® XR80015 nozzles (TeeJet Technologies, Glendale Heights, IN) spaced at 0.5 meters (20 inches).

3.2 Harvest Aid Timing

Timing trials were initiated in 2014 and repeated in 2015. Application timings consisted of an early application at 50% dry pods, and an optimal, or labeled, application at 80% dry pods. Additionally a third late, post freeze timing was planned. However, in both years the timing trials were conducted the first hard freeze lasted for four or more days with temperatures remaining below freezing for more than 24 hours at a time.

These hard freeze events were severe enough to cause a large enough effect on the rating parameters that quality data could not have been attained, and the third application was forgone. Procedures, application rates and data collection were identical to the efficacy trials. Active ingredients used in the timing trials were sodium chlorate, paraquat, and glyphosate. These active ingredients were chosen because they are labeled for use as a harvest aid in either or both guar, and dry beans. As in the efficacy trial ratings were made for color, percent green pods, percent growing terminal and regrowth. Ratings were also conducted on the same schedule of 0, 7, 14, and 28 DAT.

Texas Tech University, Jonathan Shockey, December 2016

3.3 Black Seed Measurements

Black seed measurements were taken using a Model 850 electronic seed counter

(The Old Mill Company, Annapolis Junction, MD, USA) to count and collect three, 100 seed subsamples from each sample. Each subsample was sorted by color, according to the color designations described in Liu et al. (2007) shriveled seed was also separated out in accordance with Liu et al. (2007) and counted as part of the black seed measurement.

Colors designations were black, dark grey, and light grey or tan; all seeds darker than dark grey were considered black for this measurement. The separated black and or shriveled seed was counted, and average percentages of black seed calculated for each sample.

Texas Tech University, Jonathan Shockey, December 2016

Chapter IV

Results and Discussion

4.1 Harvest Aid Efficacy

Statistical analysis determined that both year and location had no significant

effect on treatments, thus rating data for both years and all five locations were combined

for further analysis.

Baseline plant color at the 0 DAT ratings showed only a slight differences

between treatments with all plots falling in the light green (3) to green-yellow (4) range

in the color scale (Table 4.1.1; Figure 4.1.1). These ratings provided the base line by

which treatment effects could be quantified.

At 7 DAT paraquat and diquat dibromide having tan (6) to brown (7) ratings had

increased the drydown of the plants greatly (Table 4.1.1; Figure 4.1.1). Glufosinate

produced a yellow (5) to tan rating while sodium chlorate and glyphosate rated in the

green-yellow to yellow range (Table 4.1.1; Figure 4.1.1). Carfentrazone-ethyl, pyraflufen-ethyl, and the untreated control rated in the range of light-green to green-

yellow (Table 4.1.1; Figure 4.1.1). Across all trials and years the color response at 7

DAT showed that diquat dibromide, paraquat, and glufosinate have a clear effect on color

and thusly plant moisture.

At 14 DAT diquat dibromide and paraquat treated plots rated as tan to brown

having significantly desiccated the plants. Glufosinate ratings increased to 6.3, this was

above the rating of carfentrazone-ethyl (5.6), sodium chlorate (5.7), and glyphosate (5.6).

Texas Tech University, Jonathan Shockey, December 2016

Finally, pyraflufen-ethyl treated plots (4.7) and the untreated control (4.4) showed little

change (Table 4.1.1; Figure 4.1.1). These color differences seen in the 7 DAT ratings

appear in the 14 DAT ratings and show that after a single application of either paraquat,

diquat dibromide, or glufosinate guar is harvestable in one to two weeks post application

reducing the time mature seeds are exposed to environmental weathering by at least one month.

In both regions the normal hard freeze event that naturally initiates permanent guar drying occurred between the 14 and 28 DAT ratings. This occurs on average around

November, 16th in both regions (Society, 2010). Therefore, the control becomes the

reference point by which an earlier harvest using harvest aids could be obtained.

By 28 DAT the distinct grouping seen with the day 14 ratings had diminished with

paraquat, diquat dibromide, glufosinate, sodium chlorate, and glyphosate treated plots

rating in the tan to brown range. Carfentrazone-ethyl, pyraflufen-ethyl, and the untreated control remained in the yellow to tan range (Table 4.1.1; Figure 4.1.1).

While plots in four of the seven treatments had reached the tan to brown color

range and would be harvestable based on this color, the color rating for the control plots

averaged 5.4 or between green-yellow and yellow thus making control plots not yet harvestable at 28 DAT. The similarities in ratings for plots treated with paraquat, diquat dibromide, sodium chlorate, glufosinate, and glyphosate in the 28 DAT ratings is partially due to the varied speed at which these chemicals produce symptoms in treated plants, and partially due to the plant already being stressed by the harvest aid application at the time of the hard freeze event.

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Table 4.1.1 Average color ratings for each rating time post application for all treatments for all trials and all years combined.

Sodium Diquat Carfentrazone- Pyraflufen- Color Rating Glyphosate Paraquat Glufosinate Control Chlorate dibromide ethyl ethyl Average 3.8 3.8 3.8 3.7 3.9 3.8 3.8 3.8 Day 0 C. I. (0.05) 0.3 0.3 0.3 0.4 0.3 0.3 0.3 0.3 LSD (0.05) ab ab ab b ab ab a ab Average 4.3 4.2 6.3 6.4 4.9 4.2 5.3 3.9 Day 7 C. I. (0.05) 0.5 0.3 0.3 0.3 0.6 0.4 0.4 0.4 LSD (0.05) bc bc a a c c b c Average 5.7 5.6 6.7 6.8 5.6 4.7 6.3 4.4 Day 14 C. I. (0.05) 0.4 0.2 0.2 0.1 0.4 0.3 0.3 0.3 LSD (0.05) c c a a d e b e Average 6.0 6.5 6.8 7.0 5.7 5.0 6.8 5.4 Day 28 C. I. (0.05) 0.3 0.2 0.2 0.0 0.4 0.3 0.2 0.3 LSD (0.05) c b ab a d d ab d

Figure 4.1.1 Efficacy trial average color ratings for all years and locations combined by rating time (DAT).

Percent green pod measures also showed a pattern and statistical grouping between potential harvest aid active ingredients. Baseline ratings at DAT 0 showed slight statistical differences between treatments with all treatments falling in the average range of 17 to 23% green pods (Table 4.1.2; Figure 4.1.2).

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At 7 DAT measures for plots treated with paraquat, carfentrazone-ethyl, and

sodium chlorate had reduced green pod percentages markedly with values ranging from

2.5 to 7% green pods (Table 4.1.2; Figure 4.1.2). The diquat dibromide treatment is not

in the first grouping due to a large confidence interval despite having an average of 7.7%

green pods (Table 4.1.2; Figure 4.1.2).

At 14 DAT, diquat dibromide, paraquat, and glufosinate treatments all have

distinctly reduced green pod percentages, averaging less than 1% green pods, while

sodium chlorate, glyphosate, and carfentrazone-ethyl treatments with an average green

pod percentage ranging from 2 to 4% have slowed in the drying of seed pods (Table

4.1.2; Figure 4.1.2). Plots treated with sodium chlorate had a green pod percent of 2.3

was also found not different from plots treated with glufosinate, and carfentrazone-ethyl treated plots with a 3.7% green pod was found to not be different from pyraflufen-ethyl treated plots at 5.3% green pods (Table 4.1.2; Figure 4.1.2). The untreated control plots had the highest percent green pods of all treatments at 6.3% green pods at 14 DAT (Table

4.1.2; Figure 4.1.2). Percent green pod measurements also show that by 7 to 14 DAT the active ingredients paraquat, diquat dibromide, and glufosinate produce dry harvestable pods at two weeks in advance of the control in this aspect

By 28 DAT measurements for percent green pods for all chemical treatments is

0%, while the control plots retained 0.7% green pods (Table 4.1.2; Figure 4.1.2). Though having sufficiently dried pods by 28 DAT as noted before, plots within the control as well as carfentrazone-ethyl, and pyraflufen-ethyl treatments are not dry enough at the plant level to be effectively harvested due to high color scores still present (Table 4.1.2; Figure

4.1.2). As noted guar has a tendency to retain moisture in the stems after seed is mature

Texas Tech University, Jonathan Shockey, December 2016 and ready to harvest causing issues with harvest equipment and seed moistures. Percent green pod measurements at 28 DAT show evidence of this issue as all treatments including the untreated control have sufficiently dried pods for harvest though the color ratings show too much moisture in the rest of the plant to allow harvest (Table 4.1.1).

Table 4.1.2 Average green pod percent for all treatments across all years and locations combined at each rating post application.

Sodium Diquat Carfentrazone- Pyraflufen- Green Pod % Glyphosate Paraquat Glufosinate Control Chlorate dibromide ethyl ethyl Average 19.0 18.7 17.3 22.3 18.0 21.0 17.7 21.0 Day 0 C. I. (0.05) 4.2 2.7 2.0 3.0 2.9 2.3 2.4 2.8 LSD (0.05) ab ab b a b ab b ab Average 7.0 9.0 7.7 2.7 6.7 9.3 8.3 10.7 Day 7 C. I. (0.05) 2.6 2.5 5.9 1.6 1.5 1.8 2.7 2.6 LSD (0.05) ab a a b ab a a a Average 2.3 2.7 0.3 0.0 3.7 5.3 0.7 6.3 Day 14 C. I. (0.05) 1.8 1.3 0.6 0.0 1.7 1.5 0.9 1.7 LSD (0.05) cd c e e bc ab de a Average 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 Day 28 C. I. (0.05) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.3 LSD (0.05) b b b b b b b a

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Figure 4.1.2 Average green pod percent at each rating time after application of harvest aids for all efficacy trial years and locations combined.

Baseline percent terminal growth measurements ranged from 24 to 37% (Table

4.1.3; Figure 4.1.3), showing two groups statistically, with only carfentrazone-ethyl and

the control being significantly different from each other. Ratings at DAT 7 showed

substantial decrease in terminal growth with measurements ranging from 0 to 21%.

Statistical groupings were as follows: control and pyraflufen-ethyl treatments (greatest remaining growth); pyraflufen-ethyl, glufosinate, and glyphosate treatments; glufosinate, glyphosate, carfentrazone-ethyl, paraquat, diquat dibromide, and sodium chlorate treatments (Table 4.1.3; Figure 4.1.3).

By DAT 14 the active ingredients sodium chlorate, glyphosate, diquat dibromide, paraquat, carfentrazone-ethyl, pyraflufen-ethyl, and glufosinate reduced terminal growth

Texas Tech University, Jonathan Shockey, December 2016 to percentages ranging from 0 to 3% (Table 4.1.3; Figure 4.1.3). The control plots retained an average terminal percent of 17.3% (Table 4.1.3; Figure 4.1.3). Percent terminal measurements as well show that by 7 to 14 DAT paraquat, diquat dibromide, and glufosinate treatments have substantially dried the guar plants and halted terminal growth so that the crop is harvestable at this time.

There was no change in statistical groupings for 28 DAT measurements with percentages ranging from 0 to 1%, and 6% respectively (Table 4.1.3; Figure 4.1.3).

These results show that by 28 DAT and after the hard freeze event all treatments where the plants were treated with a harvest aid show minimal to no terminal growth. The control plots however still had significant terminal growth and would likely be unharvestable after only one hard freeze. In the event that temperatures were to rebound and stay above freezing this growth would continue to hinder harvest.

Table 4.1.3 Average percent terminal growth for all locations across all years for each rating post application.

Sodium Diquat Carfentrazone- Pyraflufen- Terminal % Glyphosate Paraquat Glufosinate Control Chlorate dibromide ethyl ethyl Average 31.7 26.0 26.7 29.3 24.7 32.0 27.3 36.7 Day 0 C. I. (0.05) 9.1 7.9 7.1 6.8 5.5 8.3 8.8 9.9 LSD (0.05) ab ab ab ab b ab ab a Average 1.0 9.0 0.0 0.0 2.0 13.0 5.0 20.7 Day 7 C. I. (0.05) 1.4 5.5 0.0 0.0 1.2 5.5 4.0 15.1 LSD (0.05) c bc c c c ab bc a Average 0.3 0.3 0.0 0.0 0.7 3.0 0.0 17.3 Day 14 C. I. (0.05) 0.6 0.6 0.0 0.0 0.9 2.7 0.0 15.7 LSD (0.05) b b b b b b b a Average 0.0 0.0 0.0 0.0 0.0 0.7 0.0 6.0 Day 28 C. I. (0.05) 0.0 0.0 0.0 0.0 0.0 1.3 0.0 10.1 LSD (0.05) b b b b b b b a

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Figure 4.1.3 Average estimated terminal growth percentages for all efficacy trials across all yea rs and locations.

Regrowth as defined in this study was the appearance of new growth at the nodes or junctures between the stem and branches, and was assessed at 0 DAT to establish a data baseline for regrowth at 7 DAT. Ratings at 7 DAT showed that there was no difference in regrowth, with rating ranging from 0 (none) to less than 1 (trace) (Table

4.1.4; Figure 4.1.4).

Regrowth in this study began at the lowest nodes and progressed upward through the plant so that 14 DAT ratings of carfentrazone-ethyl, pyraflufen-ethyl treatments, and the untreated control produced moderate to trace amounts of regrowth (1 to 2 rating)

(Table 4.1.4; Figure 4.1.4). Sodium chlorate, glyphosate, diquat dibromide, paraquat, and glufosinate treatments contained zero to trace amounts of regrowth (Table 4.1.4; Figure

4.1.4). Regrowth ratings showed little to no regrowth by 7 DAT; however, by 14 DAT plots treated with pyraflufen-ethyl, carfentrazone-ethyl, and the untreated control showed

Texas Tech University, Jonathan Shockey, December 2016 enough regrowth to hinder harvest. Whereas, diquat, paraquat, and even glyphosate treatments have either slowed or halted regrowth to an acceptable amount for harvest.

Glufosinate treatments contains a trace (1) amount of regrowth according to the rating scale but on average is only 0.1 and would still be harvestable (Table 4.1.4; Figure 4.1.4).

At 28 DAT there is a decrease in regrowth, with all chemical treatments containing zero to trace amounts of regrowth. Plots treated with sodium chlorate, carfentrazone-ethyl, pyraflufen-ethyl, glufosinate and the control contained trace amounts regrowth (Table 4.1.4; Figure 4.1.4). Paraquat, diquat dibromide, and glyphosate treatments had halted regrowth completely (Table 4.1.4; Figure 4.1.4). As seen with other ratings, the hard freeze event between 14 DAT and 28 DAT causes a drop in the amount of regrowth observed with only trace amounts remaining in sodium chlorate, carfentrazone-ethyl, pyraflufen-ethyl, and the control treatments. However, the presence this amount of regrowth could potentially still hinder harvest.

Table 4.1.4 Due to lack of regrowth at the date of application average regrowth ratings are given for all other rating times post application. 0 = None; 1 = Trace; 2 = Moderate; 3 = High. Regrowth declines as 28 DAT due to a hard freeze event prior to rating.

Sodium Diquat Carfentrazone- Pyraflufen- Regrowth Glyphosate Paraquat Glufosinate Control Chlorate dibromide ethyl ethyl Average 0.1 0.1 0.0 0.0 0.1 0.2 0.1 0.2 Day 7 C. I. (0.05) 0.1 0.2 0.0 0.0 0.2 0.2 0.1 0.2 LSD (0.05) a a a a a a a a Average 0.3 0.0 0.0 0.0 0.9 1.0 0.1 1.2 Day 14 C. I. (0.05) 0.2 0.0 0.0 0.0 0.4 0.4 0.1 0.5 LSD (0.05) b b b b a a b a Average 0.1 0.0 0.0 0.0 0.3 0.4 0.1 0.3 Day 28 C. I. (0.05) 0.2 0.0 0.0 0.0 0.3 0.2 0.1 0.3 LSD (0.05) abc c c c ab a bc abc

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Figure 4.1.4 Average regrowth ratings for efficacy trials across all years and locations.

Yields for the efficacy trials were significantly different across both years and all

five locations due to environmental effects. However, when compared to the control both

yield and bushel weight were not different alpha = 0.05, across all treatments when data

from all years and all locations are combined (Table 4.1.5; Figure 4.1.5). Also to be

considered, all treatments were harvested at the same time within a location though many

were harvestable before the 28 DAT ratings. Thus future research should omit the 28

DAT ratings and harvest each treatment as it becomes harvestable; by doing this a clear difference and pattern of difference in yields could potentially occur either in favor of harvest aid use or against.

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Table 4.1.5 Average bushel weight and average kg per hectare for all locations and years combined. Sodium Diquat Carfentrazone- Pyraflufen- Bushel Weight Glyphosate Paraquat Glufosinate Control Chlorate dibromide ethyl ethyl Average 57.0 55.4 55.4 55.1 56.3 56.3 55.3 55.3 C. I. (0.05) 2.7 1.9 2.7 2.5 2.1 2.2 2.6 2.7 LSD (0.05) a a a a a a a a

Sodium Diquat Carfentrazone- Pyraflufen- kg/hectare Glyphosate Paraquat Glufosinate Control Chlorate dibromide ethyl ethyl Average 670 614 588 560 614 622 576 657 C. I. (0.05) 130 94 83 81 70 104 79 122 LSD (0.05) a a a a a a a a

Figure 4.1.5 Average yield data in both bushel weight and kilograms per hectare for all efficacy trial across all years and locations combined.

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4.2 Harvest Aid Timing Results

Data for Timing trials was analyzed with the same techniques as the efficacy

trials. Visual ratings and changes were consistent across years and locations and

therefore were combined for analysis.

4.2.1 Early Application Results

Baseline color ratings at DAT 0 for the early application showed no statistical

difference with ratings ranging from 2.3 to 2.7, or in the light to medium green range

(Table 4.2.1.1; Figure 4.2.1.1). By DAT 7 paraquat treatments had increased color

ratings significantly from the other treatments with a 5.7 (yellow to tan) color rating as

compared to the 3.3 rating of the control. While the other three treatments showed no

difference and ranged from 3.3 to 3.8 (light green to green-yellow) (Table 4.2.1.1; Figure

4.2.1.1). DAT 14 ratings still showed paraquat treatments to outperform all other

treatments averaging 6.5 color rating or tan to brown in color. Glyphosate treated plots

also began to have a greater color score than all other treatments with an average 5.2

rating or yellow to tan color (Table 4.2.1.1; Figure 4.2.1.1). Additionally analysis

showed that sodium chlorate treatments and the untreated control were not significantly

different with average color ratings ranging from 3.8 to 4.1 or light green to green-yellow

in color (Table 4.2.1.1; Figure 4.2.1.1). Finally, DAT 28 ratings showed paraquat and

glyphosate treatments to equal to each other with average color rating ranging from 6.1 to

6.6 of in the tan color range, while sodium chlorate treatments and the untreated control color ratings have become almost stagnant with average ratings ranging from 4.5-5.1 or green-yellow to yellow in color (Table 4.2.1.1; Figure 4.2.1.1).

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As seen in the efficacy trials paraquat treatments performed well producing plants that were dry enough to harvest by the 14 to 28 day ratings. Glyphosate treatments performed better than sodium chlorate treatments in this same time frame, but were not able to produce harvestable plants until 28 DAT. Sodium chlorate had by 28 DAT still not produced a harvestable plant and was only slightly drier than the control. This could potentially be due to the increased foliage present with early applications that is not present at optimal spray timing due to the morphology of the guar plant.

Table 4.2.1.1 Average color ratings for early harvest aid applications at each rating time across all trials and years.

Sodium Color Rating Glyphosate Paraquat Control Chlorate Average 2.7 2.5 2.3 2.5 Day 0 C. I. (0.05) 0.4 0.3 0.3 0.4 LSD (0.05) a a a a Average 3.8 3.8 5.8 3.3 Day 7 C. I. (0.05) 0.4 0.5 0.2 0.4 LSD (0.05) b b a b Average 4.2 5.2 6.6 3.7 Day 14 C. I. (0.05) 0.6 0.3 0.4 0.3 LSD (0.05) bc b a c Average 5.1 6.1 6.8 4.3 Day 28 C. I. (0.05) 0.6 0.3 0.3 0.4 LSD (0.05) b a a b

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Figure 4.2.1.1 Average color ratings for all early harvest aid applications across all years and locations by DAT.

Percent green pods baseline measurements showed no difference across treatments at DAT 0 with average percentages ranging from 46 to 49% (Table 4.2.1.2;

Figure 4.2.1.2). By 7 DAT sodium chlorate and paraquat treatments with average percentages ranging from 5.8 to 15.8% green pods had decreased the percent green pods held by the plant significantly (Table 4.2.1.2; Figure 4.2.1.2). Sodium chlorate, glyphosate treatments, and the untreated control also showed no difference from one another with average percent green pods ranging from 15.8 to 24.6% (Table 4.2.1.2;

Figure 4.2.1.2). Percent green pods measured at DAT 14 revealed paraquat treatments to be lower than all other treatments with average percent green pods of 0.8% (Table

4.2.1.2; Figure 4.2.1.2). Also, plots treated with sodium chlorate and glyphosate were not significantly different from one another with average percent green pods ranging from

4.2 to 5.4%.; while the untreated control was found to be higher than all other treatments

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with an average percent green pods of 8.3% (Table 4.2.1.2; Figure 4.2.1.2). Plots treated

with glyphosate and paraquat at 28 DAT were similar with the lowest percent green pod

measures ranging from .4-1.3%, also glyphosate and sodium chlorate treatments showed

no difference with average percent green pods ranging from 1.3-3.3% (Table 4.2.1.2;

Figure 4.2.1.2). Finally, DAT 28 measurements for percent green pods showed sodium chlorate treatments had not significantly affected the percent green pods when compared to the untreated control both having percent green pod measures ranging from 3.3 to

4.6% (Table 4.2.1.2; Figure 4.2.1.2).

Paraquat when applied early drastically reduced green pod percentages by 14

DAT. This is slower than that observed in the efficacy and optimal trials, having higher percent green pods at 7 DAT than the other trials. Despite this slow start by 14 DAT the green pods are all equal between timings of application. This delay in effect on pods could potentially be due to the growth stage of the plant as there were both more foliage and green pods at the time of application. Overall glyphosate treatments did not dry the pods enough for harvest until 28 DAT this is a substantial amount of time for harvestable yield to be subject to environmental weathering. Sodium chlorate treatments and the control still contained far too many green pods to be harvestable at 28 DAT and would require other actions or more time in the field to be harvestable.

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Table 4.2.1.2 Average estimated green pod percentages for early harvest aid applications across all trials and locations combined. Sodium Green Pod % Glyphosate Paraquat Control Chlorate Average 46.7 48.3 48.3 45.8 Day 0 C. I. (0.05) 6.3 7.2 6.0 6.3 LSD (0.05) a a a a Average 15.8 20.8 6.7 23.8 Day 7 C. I. (0.05) 5.4 8.2 7.4 8.1 LSD (0.05) b b a b Average 5.4 3.8 0.4 9.2 Day 14 C. I. (0.05) 1.8 1.7 0.8 1.1 LSD (0.05) bc b a c Average 3.3 0.4 0.8 5.0 Day 28 C. I. (0.05) 1.8 0.8 1.6 1.6 LSD (0.05) b a a b

Figure 4.2.1.2 Average percent growing terminal for early harvest aid application timings

across all trial and locations by DAT.

Baseline percent terminal measurements for the early harvest aid timing applications showed no difference across treatments at 0 DAT (Table 4.2.1.3; Figure

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4.2.1.3). After treatment paraquat and sodium chlorate had reduced the growing terminal substantially by 7 DAT with terminal percent ranging from 0.0 to 2.5% (Table 4.2.1.3;

Figure 4.2.1.3). Glyphosate treatments had also reduced the growing terminal measures though not as drastically, retaining 15.4% growing terminal. The untreated control had

41.7% of the growing terminal remaining (Table 4.2.1.3; Figure 4.2.1.3). Measurements for treatments at DAT 14 showed paraquat (0.0%) and glyphosate (0.8%) similar to sodium chlorate which remained unchanged at 2.5% (Table 4.2.1.3; Figure 4.2.1.3). The control at DAT 14 had notably remaining terminal growth (13.8%). By 28 DAT both paraquat and glyphosate treatments contained 0.0% growing terminals while sodium chlorate treatments had increased slightly to 2.9% terminal and was found to not be statistically different from paraquat and glyphosate treatment as well as the control

(4.2%) (Table 4.2.1.3; Figure 4.2.1.3).

Terminal percent measurements showed that paraquat applications had halted terminal growth to a point that would be harvestable by 7 DAT. While applications of glyphosate became harvestable at 14 DAT, and sodium chlorate treatments and the untreated control were not harvestable by the 28 DAT ratings, requiring other action to be taken to allow for harvest of these treatments, either a second application or a hard freeze.

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Table 4.2.1.3 Average estimated percent growing terminal for early harvest aid applications across all trials and locations by DAT.

Sodium Terminal % Glyphosate Paraquat Control Chlorate Average 87.5 91.7 97.1 92.5 Day 0 C. I. (0.05) 14.6 8.3 3.4 7.0 LSD (0.05) a a a a Average 2.5 15.4 0.0 41.7 Day 7 C. I. (0.05) 3.9 12.2 0.0 20.1 LSD (0.05) c b c a Average 2.5 0.8 0.0 13.8 Day 14 C. I. (0.05) 3.2 1.6 0.0 8.3 LSD (0.05) b b b a Average 2.9 0.0 0.0 4.2 Day 28 C. I. (0.05) 3.4 0.0 0.0 3.4 LSD (0.05) ab b b a

Figure 4.2.1.3 Average estimated percent terminal for early harvest aid applications across all trials and years by DAT.

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Regrowth at the nodes of the plant in the early timing plots did not begin until 14

DAT. At this time both paraquat and glyphosate had a regrowth rating of 0.0 or no

regrowth (Table 4.2.1.4; Figure 4.2.1.4). Treatments of sodium chlorate and the control

both contained trace amounts of regrowth with ratings of 0.2 and 0.5 respectively (Table

4.2.1.4; Figure 4.2.1.4). At the 28 DAT rating both paraquat and glyphosate treatments

contained trace amounts of regrowth with ratings of 0.1 and 0.3 respectively, while

treatments of sodium chlorate and the untreated control had moderate amounts of

regrowth with ratings of 1.2 and 1.3 respectively (Table 4.2.1.4; Figure 4.2.1.4).

Regrowth ratings showed that no regrowth was observed in any treatment until 14 days after the application, at this time both the control and sodium chlorate treatments contained trace amounts of regrowth that would affect moisture content of seed harvested, while glyphosate and paraquat applications still halted regrowth at this time.

However, by 28 DAT all treatments contained enough regrowth to hinder harvest.

Table 4.2.1.4 Average regrowth ratings for early harvest aid applications across all trials and years by DAT. 0 = None; 1 = Trace; 2 = Moderate; 3 = High.

Sodium Regrowth Glyphosate Paraquat Control Chlorate Average 0.2 0.0 0.0 0.5 Day 14 C. I. (0.05) 0.2 0.0 0.0 0.3 LSD (0.05) ab b b a Average 1.2 0.3 0.1 1.3 Day 28 C. I. (0.05) 0.6 0.2 0.2 0.5 LSD (0.05) a b b a

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Figure 4.2.1.4 Average regrowth ratings for early harvest aid applications across all years and locations by DAT.

Though the active ingredients paraquat and glyphosate performed well in drying the plants with respect to drydown as represented by plant color change and lack of terminal growth at 14 DAT due to the retention of green pods, as well as the appearance of regrowth these treatments and especially sodium chlorate would require a second application to complete the drying process and allow for earlier harvest. Since the profitability of guar is much lower than most other crops grown in the Texas High and

Rolling Plains a second application of harvest aids is another input that further reduces profitability and would not be in the producer’s best interest. Therefore, this research shows suggests there is no advantage to early application of harvest aids in guar based on plant color, terminal growth, and especially regrowth.

4.2.2 Optimal Timing Application Results

Optimal timing applications targeted the point in crop maturity where 80% of the pods were dry and brown; this is also the timing at which the efficacy trials targeted. Due to this overlap in timing of application data for the optimal timing applications closely follows that of the efficacy trials.

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Baseline color ratings for optimal application timings at 0 DAT showed no statistical differences with among plots having an average color rating in the 3 to 4 color range (Table 4.2.2.1; Figure 4.2.2.1). Ratings at 7 DAT showed that the active ingredients paraquat (5.8) and glyphosate (4.3) to have increased the color score largely over the untreated control. Sodium chlorate treatments (3.7) had no color change relative to the control (3.6) (Table 4.2.2.1; Figure 4.2.2.1). Paraquat treatments at 14 DAT were different from all other treatments with an elevated color rating of 6.6, while sodium chlorate and glyphosate treatments were grouped together with average color ratings of

5.0 and 5.4 respectively (Table 4.2.2.1; Figure 4.2.2.1). Finally, at 14 DAT the untreated control was found to be significantly less (4.1) (Table 4.2.2.1; Figure 4.2.2.1). Color ratings for 28 DAT applications of paraquat and glyphosate had increased average color ratings of 6.9 and 6.4 respectively (Table 4.2.2.1; Figure 4.2.2.1). Sodium chlorate treatments and the untreated control averaged 5.3 and 5.2 respectively (Table 4.2.2.1;

Figure 4.2.2.1).

Color ratings for optimal timing applications showed that by 7 to 14 days post application paraquat produced an average color rating that would suggest earlier harvest is possible at that time. Glyphosate applications had a potentially harvestable color score by 28 DAT; however, this represents an additional two weeks mature seed is subject to environmental weathering as compared to paraquat applications. Other treatments were much slower in drying and as in the case of the control and the active ingredient sodium chlorate, plots were still not dry enough to harvest after a hard freeze event occurred prior to the 28 day ratings.

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Table 4.2.2.1 Average color ratings for optimal harvest aid applications at each rating time across all trials and years. Sodium Color Rating Glyphosate Paraquat Control Chlorate Average 3.5 3.8 3.7 3.6 Day 0 C. I. (0.05) 0.4 0.3 0.4 0.4 LSD (0.05) a a a a Average 3.7 4.3 5.8 3.6 Day 7 C. I. (0.05) 0.5 0.4 0.3 0.4 LSD (0.05) c b a c Average 5.0 5.4 6.6 4.1 Day 14 C. I. (0.05) 0.3 0.4 0.3 0.4 LSD (0.05) b b a c Average 5.3 6.4 6.9 5.3 Day 28 C. I. (0.05) 0.5 0.4 0.2 0.3 LSD (0.05) b a a b

Figure 4.2.2.1 Average color ratings for all optimal harvest aid applications across all years and locations by DAT.

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Baseline percent green pod measures at 0 DAT for optimal spray timing showed as slight differences with average percentages ranging from 18.8 to 20.0% green pods

(Table 4.2.2.2; Figure 4.2.2.2). Measurements for 7 DAT showed paraquat treatments to have an average of 2.5% green pods, substantially lower than treatments of sodium chlorate, glyphosate and the untreated control (6.7, 7.0, and 7.9%, respectively; Table

4.2.2.2; Figure 4.2.2.2). Green pod percent measures at 14 DAT show that paraquat treatments dried all remaining green pods, and was drastically lower than all other treatments (Table 4.2.2.2; Figure 4.2.2.2). While treatments of sodium chlorate and glyphosate were found to be similar with average green pod percent scores of 4.1 and

2.9% respectively (Table 4.2.2.2; Figure 4.2.2.2). At 28 DAT all chemical treatments had 0.0% green pods, and with only a few green pods remaining in the control (0.4%;

Table 4.2.2.2; Figure 4.2.2.2).

Results of the percent green pod measurements for the optimal time showed that by 14 DAT the active ingredient paraquat had dried the pods sufficiently to allow harvest of the crop. However, for all other treatments it was not until a hard freeze event before the 28 DAT measurements that green pod percentages were low enough to not negatively affect moisture at harvest. This data much like the efficacy data shows that one application of paraquat can accelerate drying and allow for harvest up to one month earlier than natural drying alone drastically shortening the time harvestable yield is subjected to environmental weathering.

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Table 4.2.2.2 Average estimated green pod percentages for optimal harvest aid applications across all trials and locations combined.

Sodium Green Pod % Glyphosate Paraquat Control Chlorate Average 20.0 18.8 18.8 19.6 Day 0 C. I. (0.05) 4.6 2.3 1.7 1.8 LSD (0.05) a a a a Average 6.7 7.1 2.5 7.9 Day 7 C. I. (0.05) 2.1 1.8 1.8 1.4 LSD (0.05) a a b a Average 4.2 2.9 0.0 6.7 Day 14 C. I. (0.05) 2.3 1.4 0.0 2.1 LSD (0.05) ab b c a Average 0.0 0.0 0.0 0.4 Day 28 C. I. (0.05) 0.0 0.0 0.0 0.8 LSD (0.05) a a a a

Figure 4.3.2 Average estimated percent growing terminal for optimal harvest aid application timings across all trial and locations by DAT.

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Baseline percent terminal measurements for optimal application timing at 0 DAT contained differences with treatments of glyphosate, paraquat and the untreated control having statistically similar average measurements falling in the 24 to 40% range, and sodium chlorate treatments had an average terminal percentage of 42.5 and were found to not be different from that of paraquat treatments or the untreated control (Table 4.2.2.3;

Figure 4.2.2.3). These initial differences in terminal growth are due to agronomic management practices, for example irrigated versus dryland cropping; the 2015 dryland trials had much lower terminal growth than the irrigated trial. At 7 DAT treatments of paraquat, glyphosate, and sodium chlorate had reduced terminal growth markedly (1.2,

9.5, and 0.0% respectively) from the untreated control (22.5%; Table 4.2.2.3; Figure

4.2.2.3). By 14 DAT applications of paraquat (0.0%), glyphosate (0.4%), and sodium chlorate (0.4%) stopped all terminal growth (Table 4.2.2.3; Figure 4.2.2.3). The untreated control retained significantly greater terminal growth at 14 DAT (13.3%; Table

4.2.2.3; Figure 4.2.2.3). Percent terminal scores for 28 DAT remain unchanged statistically from each other compared to the results at 14 DAT (Table 4.2.2.3; Figure

4.2.2.3).

Analysis of percent terminal growth showed that by DAT 7 the active ingredient paraquat had halted all terminal growth within the crop and would be harvestable by this time post application. Sodium chlorate and glyphosate applications had halted terminal to a point that harvest could occur by 14 DAT. The untreated control retained sufficient terminal growth to hinder harvest after the hard freeze event occurring prior to the 28

DAT ratings.

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Table 4.2.2.3 Average estimated percent terminal growth for optimal harvest aid applications across all trials and locations by DAT.

Sodium Terminal % Glyphosate Paraquat Control Chlorate Average 42.5 24.6 26.7 40.0 Day 0 C. I. (0.05) 15.0 8.3 6.3 12.0 LSD (0.05) a b ab ab Average 1.3 9.6 0.0 22.5 Day 7 C. I. (0.05) 1.7 6.8 0.0 13.9 LSD (0.05) b b b a Average 4.2 2.9 0.0 6.7 Day 14 C. I. (0.05) 2.3 1.4 0.0 2.1 LSD (0.05) ab b c a Average 0.0 0.0 0.0 2.1 Day 28 C. I. (0.05) 0.0 0.0 0.0 2.1 LSD (0.05) b b b a

Figure 4.2.2.3 Average estimated percent terminal for optimal harvest aid applications across all trials and years by DAT.

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Regrowth rating for the optimal application timing trials much like the efficacy trials showed no regrowth at 0 DAT and thus this rating became the baseline to which all other regrowth ratings were compared. Regrowth ratings for 7 DAT showed only slight regrowth with average rating ranging from 0 to 0.3 (Table 4.2.2.4; Figure 4.2.2.4).

Rating for DAT 14 glyphosate and paraquat treatments had little to no regrowth (0.0 and

0.1 respectively; Table 4.2.2.4; Figure 4.2.2.4). Sodium chlorate treatments (0.5) had slightly more regrowth, while the untreated control (1.5) contained trace to moderate amounts of new growth at the nodes (Table 4.2.2.4; Figure 4.2.2.4). At 28 days post application regrowth ratings showed treatments of paraquat, 0.0, glyphosate, 0.0, and sodium chlorate, 0.3, to have significantly slowed regrowth (Table 4.2.2.4; Figure

4.2.2.4). The untreated control (0.4) had also decreased in regrowth due to the hard freeze (Table 4.2.2.4; Figure 4.2.2.4).

Regrowth ratings at 7 DAT showed that applications of paraquat had halted regrowth to a point that the crop could be harvested. However, a trace amount of regrowth begins to appear in paraquat treatments by 14 DAT though the crop would still be harvestable with this trace amount without much effect to seed moisture. Regrowth rating for the optimal application timing also showed that an application of glyphosate has the ability to halt regrowth throughout the entire rating timeframe, although due to average color and green pod score glyphosate treated plots do not become harvestable until after the hard freeze. Sodium chlorate applications also slowed regrowth to a point that would be harvestable, but due to color ratings would still not be harvestable at 28

DAT. The untreated control retained enough regrowth at 28 DAT ratings to hinder harvest and significantly affect seed moisture.

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Table 4.2.2.4 Average regrowth ratings for optimal harvest aid applications across all trials and years by DAT. 0 = None; 1 = Trace; 2 = Moderate; 3 = High.

Sodium Regrowth Rating Glyphosate Paraquat Control Chlorate Average 0.1 0.2 0.0 0.3 7 DPA C. I. (0.05) 0.2 0.2 0.0 0.2 LSD (0.05) a a a a Average 0.5 0.0 0.2 1.5 14 DPA C. I. (0.05) 0.3 0.0 0.2 0.5 LSD (0.05) b c bc a Average 0.3 0.0 0.0 0.4 28 DPA C. I. (0.05) 0.3 0.0 0.0 0.4 LSD (0.05) ab b b a

Figure 4.2.2.4 Average regrowth ratings for optimal harvest aid applications across all years and locations by DAT.

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As with efficacy trials, yield data collected in the timing trials showed statistical

differences between location and year due to management practices and other

environmental factors. This data, however, when compared by treatment showed no

significant difference in either bushel weight or kilograms per hectare across treatments or timings (Table 4.2.2.5; Figure 4.2.2.5).

Table 4.2.2.5 Average bushel weight and average kg per hectare for both early and optimal application timings across all locations and years combined.

Sodium Chlorate Glyphosate Paraquat Control Bushel Weight Early Optimal Early Optimal Early Optimal Early Optimal Average 56.4 56.5 55.3 56.0 55.1 56.5 56.8 56.6 C. I. (0.05) 1.9 3.0 1.2 2.0 1.2 2.2 1.2 2.7 LSD (0.05) a a a a a a a a

Sodium Chlorate Glyphosate Paraquat Control kg/Hectare Early Optimal Early Optimal Early Optimal Early Optimal Average 545 646 618 569 563 540 608 608 C. I. (0.05) 85 159 94 102 82 97 66 138 LSD (0.05) a a a a a a a a

Figure 4.2.2.5 Average yield data in both bushel weight and kilograms per hectare for both early and optimal application timings across all years and locations combined.

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4.3 Black Seed Results

Black seed percentages differed significantly across both year and location.

However, no clear pattern emerged when the data was analyzed by location therefore to

assess differences that could be attributed to treatments all data was combined. Efficacy

data, though different across year and location, showed no statistical difference between

treatments (P = 0.72). Although it appears that several harvest-aid treatments may have reduced percent black seed as numerically there were about 24 to 25% versus the control at 33% black seed, due to the lack of significant difference between treatments at the alpha 0.05 level it was determined there was no treatment effect on black seed content, and that this factor is driven primarily by the environment (Table 4.3.1; Figure 4.3.1).

Table 4.3.1 Average black seed percentages for harvest aid efficacy trials across all locations and years.

Efficacy Black Sodium Diquat Carfentrazone- Pyraflufen- Glyphosate Paraquat Glufosinate Control Seed % Chlorate dibromide ethyl ethyl Average 31.4 26.9 25.4 28.4 24.6 24.3 24.6 33.5 C. I. (0.05) 10.4 7.4 6.2 8.4 6.6 6.1 7.4 10.8 LSD (0.05) a a a a a a a a

Firgure 4.3.1 Average black seed percentages for harvest aid efficacy trials across all locations and years.

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Black seed percentages for the timing trials showed again statistical differences between location and year. However, as with efficacy results there was no clear pattern that could be attributed to the treatments (Table 4.3.2; Figure 4.3.2).

Table 4.3.2 Average black seed percentages for harvest aid timing trials both early and optimal harvest aid application timings across all locations and years.

Timing Black Sodium Chlorate Glyphosate Paraquat Control Seed % Early Optimal Early Optimal Early Optimal Early Optimal Average 29.6 38.3 36.4 32.6 37.5 33.9 36.1 41.7 C. I. (0.05) 9.4 9.6 12.5 5.8 11.1 7.8 11.3 9.8 LSD (0.05) a a a a a a a a

Figure 4.3.2 Average black seed percentages for harvest aid timing trials both early and optimal harvest aid application timings across all locations and years.

As well, it should be noted that according to the docking scale for contracted guar seed with Guar Resources LLC. Brownfield, Texas, the level of black seed found in all trials was below the lowest dockage level of 50% black seed (G. R. Staff, 2016). A possible consideration is that all plots within a trial were harvested at the same time, thus

Texas Tech University, Jonathan Shockey, December 2016 leaving all seed subject to the same environmental effects. Future studies should again forego the 28 DAT rating and harvest treatments as they become harvestable. This practice could potentially show differences in treatment effect due to either extended or reduced time seed spends in the field subjected to environmental weathering.

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Chapter V

Conclusions

The objectives of this study were first to evaluate options for herbicides that could be used as harvest aids in guar in addition to the currently labeled harvest aid herbicides

(paraquat and sodium chlorate). The second objective of this study was to experiment with application timing to determine if there would be any advantage to making early applications of harvest aids for producers. Guar is an indeterminate drought tolerant crop that is well adapted to arid and semi-arid climates like those found in the Texas plains.

Guar works well in rotations with other crops, like cotton, grown in this region by increasing yields of the following year’s crops (Trostle, 2013a). The need for harvest aids in guar is primarily due to the indeterminate nature of the crop. Guar will continue to grow as long as conditions are favorable as well as continue to remain green and moist especially in the stems, which delays harvest even after a hard freeze that would normally halt growth in most annual crops.

Yet another issue facing guar producers is the occurrence of black seed within the harvested portion of the crop. This black seed does not process as cleanly as buff or light colored seed when split to remove the galactomannan rich endosperm; because of this difficulty guar processing companies apply price penalties to guar shipments containing high amounts black seed. The discoloration of the seed is due to environmental weathering brought about by prolonged time mature seed spends in the field before harvest. This is yet another obstacle facing United States guar production that could be lessened by the use of harvest aids to allow for earlier harvest of guar crops.

Texas Tech University, Jonathan Shockey, December 2016

This research suggests that not only can a labeled harvest aid, paraquat, sufficiently dry guar crops up to a month sooner than allowing crops to naturally dry after a freeze, there are also two unlabeled herbicides, diquat dibromide and glufosinate, that perform as well as paraquat, and potential label changes adding a harvest aid application for guar should be investigated for these chemicals. These chemicals are also safer for the individual handling and applying them than paraquat. Glufosinate, however, has a preharvest interval of 70 days and would require research to determine the safety of harvested seed and end products before it could be used as a harvest aid in guar.

Additionally, it was determined that there was no effect on either yield or black seed percentages that could be attributed to harvest aid applications. However, in order to determine the full effect of each herbicide as a harvest aid and to allow ample time for both a hard freeze event and regrowth to occur rating were conducted through 28 days post application. Thus, due to this needed data harvestable yield in many plots was allowed to weather two to three weeks longer than if it were harvested when the plants were sufficiently dried. In the future to potentially observe differences in yield and black seed measurements plots should be harvested once each treatment is dried and harvestable. This practice should allow for a more clear determination of the potential benefits of harvest aid applications in guar.

Texas Tech University, Jonathan Shockey, December 2016

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